统一电能质量控制器的研究

讨论了一种统一电能质量控制器的拓扑结构,介绍了它的工作原理、补偿指令的产生方法和控制策略。其中串联有源电力滤波器被控制为电压源,并联有源电力滤波器被控制为电流源,使得负载电压为正弦电压,电网输入电流为正弦电流。在理论分析的基础上,应用MATLAB6.5软件对三相三线系统进行了仿真研究,结果表明统一电能质量控制器可有效地补偿电网侧和负载侧产生的多种电能质量问题。     

基于p-q-r理论的UPQC直接控制策略

阐述了p-q-r瞬时功率理论的原理,提出了基于该理论的统一电能质量控制器(UPQC)的直接控制策略,探讨了将其用于三相四线非线性及不平衡系统中的实现方法。着重介绍了p-q-r参考波形的产生方法,以及串联补偿电流和并联补偿电压的计算方法,并将其应用于非线性不平衡负载在电源电压不平衡及电压跌落情况下UPQC直接控制策略中。分析了控制策略的原理,推导出相关运算公式,给出了详细的控制框图。Matlab/Simulink仿真结果表明,采用该方法可以有效地消除非线性及不平衡负载对电网的影响,使电网输入功率因数为1,同时,串联补偿器隔离了电网电压对负载电压的扰动,并联补偿器给负载提供三相平衡及正弦的额定电压,不受电网电压变化的影响。     

改善微网电能质量的有源电能质量调节器研究

提出在微网交流母线和低压配网公共连接点之间并入有源电能质量调节器,可改善微网电能质量,减小微网接入对低压配网电能质量的影响.提出了基于瞬时无功理论的同步锁相方法,准确分解出公共连接点电压基波正序分量,进而求得其相位.由补偿电流控制策略计算得到参考电流,控制有源电能质量调节器实时向微网补偿谐波电流和无功电流,即使在三相负载不平衡时,使公共连接点三相电流平衡且为正弦波,从而平衡公共耦合点的三相电压.Matlab/Simulink 仿真结果证明了所提同步锁相方法和补偿电流控制策略的有效性     

三相四线UPQC系统的串联变流器控制策略

研究了三相四线统一电能质量调节器（UPQC）系统的串联变流器控制策略，该策略将串联变流器控制为正弦电流源，通过在静止ABC坐标系下对串联变流器三相输入电流分别进行独立控制，实现了电网输入电压非正弦、不平衡条件下的三相输入电流的基本平衡与正弦，且直流母线 2组电容电压稳定平衡。实验结果表明该控制策略是有效的，为三相四线UPQC系统对电网侧电能质量的改善及其并联变流器的正常运行提供了可靠的保障。     

Comparison of control strategies for DSTATCOM in three-phase,four-wire distribution system for power quality improvement under various source voltage and load conditions

This paper presents comparison of three different control strategies to generate reference current components for Distribution Static Compensator (DSTATCOM). Reference currents are tracked by a three-phase voltage source converter in a hysteresis band control scheme. These methods are instantaneous reactive power (IRP) theory, symmetrical component (SC) theory and an improved instantaneous active and reactive current component (IARCC) theory. The performance of three methods has been evaluated under various source voltage and load conditions with new IEEE Standard 1459 power definitions. A comparative study of their performance in terms of rms value of source current, Total Harmonic Distortion (THD), supply power factor and compensator ratings is also presented. A three-phase, four-wire distribution system supplying linear as well as non-linear load is considered for simulation study which is carried out using MATLAB/SIMULINK software. Under balanced and sinusoidal source voltage conditions, all three control strategies similar performance while an improved IARCC theory outperforms, particularly, under unbalanced and distorted source voltage conditions.     

Load compensation using DSTATCOM in three-phase,three-wire distribution system under various source voltage and delta connected load conditions

This paper deals with a Distribution STATic COMpensator (DSTATCOM) for balancing of source currents, power factor correction and harmonic mitigation in three-phase, three-wire distribution system supplying delta connected load under various source voltage conditions. The control strategy applied to the DSTATCOM play a major role in its performance. A novel approach based on an improved instantaneous active and reactive current component (IARCC) theory is proposed for generation of three-phase reference currents for DSTATCOM. A three-phase voltage source converter with a dc bus capacitor is employed as DSTACOM which will track the reference currents in a hysteresis band scheme. The performance of DSTATCOM is evaluated under sinusoidal, unbalanced sinusoidal and unbalanced distorted source voltage conditions. Variation in load current, variation in magnitude and harmonic content in source voltage has been considered. Delta connected linear as well as non-linear load conditions have been considered. The performance of the DSTATCOM using the proposed control strategy is demonstrated using simulation results in MATLAB/SIMULINK software. Simulation results demonstrate the feasibility of proposed scheme for the control of DSTACOM.     

Power quality enhancement using fuzzy sliding mode based pulse width modulation control strategy for unified power quality conditioner

This paper proposes a fixed switching methodology based on fuzzy sliding mode pulse width modulation (FSMPWM) control strategy for three-phase three-wire unified power quality conditioner (UPQC). The proposed FSMPWM control technique eliminates numerous power quality (PQ) problems such as current harmonics, load unbalance, voltage sag/swell, voltage unbalance, voltage distortion and phase-angle jump existing in the power distribution network. Initially, the design of FSMPWM is based on the implementation of sliding surface by proper extraction of reference current and voltage signals for UPQC. Subsequently, the equivalent control law is formulated for both shunt and series converter. With this consideration, Mamdani fuzzy rule base is designed at the sliding surface for generation of switching pulse. Moreover, the proposed method eliminates the chattering effects by smoothing the control law in a narrow boundary layer for generating fixed switching pulse for both shunt and series converter. The performance of proposed UPQC system has been simulated and analyzed by MATLAB/SIMULINK followed by real-time experimental studies accomplished with a real-time-hardware-in the loop (HIL) system in OPAL-RT simulator. Additionally, the efficacy of this proposed technique is compared with a conventional sliding mode controller (CSMC).     

统一电能质量控制器控制策略研究

该文讨论了一种统一电能质量控制器，分析了其内部的有功功率平衡。在这个基础上提出了一种基于两相同步旋转d-q坐标系的控制方案。在这种控制方案中串联电力有源滤波器被控为电流源使得输入电流为正弦，而并联电力有源滤波器被控为电压源使得负载端为标准正弦电压。最后利用仿真和实验验证了在UPQC中采用这种控制方式的有效性。     

A new control approach to three-phase active filter for harmonicsand reactive power compensation

This paper deals with a new control scheme for a parallel 3-phase active filter to eliminate harmonics and to compensate the reactive power of the nonlinear loads. A 3-phase voltage source inverter bridge with a DC bus capacitor is used as an active filter (AF). A hysteresis based carrierless PWM current control is employed to derive the switching signals to the AF. Source reference currents are derived using load currents, DC bus voltage and source voltage. The command currents of the AF are derived using source reference and load currents. A 3-phase diode rectifier with capacitive loading is employed as the nonlinear load. The AF is found effective to meet IEEE-519 standard recommendations on the harmonics level     

基于简化p-q-r理论的统一电能质量调节器控制策略

阐述了p-q-r瞬时功率理论的原理，提出一种特殊情况下的简化p-q-r理论，基于这一理论，提出一种统一电能质量调节器(unified power quality conditioner, UPQC)的综合控制策略，此策略综合了通常的直接控制策略和间接控制策略的特点。重点介绍了补偿电流及补偿电压的计算方法，详细分析了控制策略的原理，推导出p-q-r坐标下的相关运算公式，给出了在该坐标轴上的详细控制框图。仿真结果显示，将采用这种控制策略的UPQC用于补偿三相四线非线性及不平衡系统，可以实现对负载谐波、无功及中线电流较好的补偿，使负载获得额定端电压，同时提高电源侧功率因数，表明这种控制策略是可行、有效的。     

统一电能质量调节器的结构及控制策略综述

统一电能质量调节器（UPQC）能够解决多数电能质量问题,受到国内外电力研究者的广泛关注。对当前UPQC的拓扑结构类型和控制方法进行了综述。一方面,以物理结构为原则从逆变器的功能结构、供电系统方式、装置的系统配置及装置的直流母线电压的提供方式4个方面对UPQC的电路结构进行分类与综述;另一方面,将UPQC的控制部分分为3层:以补偿目标为基础的上层系统级、实施控制目标的中层装置级以及将调制信号产生脉冲的底层器件级,并针对这3层进行综述,最后探讨了UPQC的发展前景及存在的若干问题。     

基于二次线性调节器的统一电能质量控制器

在分析统一电能质量控制器系统结构和工作原理的基础上，根据UPQC的补偿目标，通过建立其状态空间模型，提出了基于二次线性最优控制的开关控制策略来跟踪电压和电流的指定值。电压和电流的基波分量采用全波移动均值提取傅里叶级数基波序分量的方法得到。利用所提方法对负载电流及电网电压畸变进行了计算机仿真，结果证明了所提方法的正确性。     

适用于双馈风电系统的九开关型统一电能质量调节器

为减小电压谐波、电压跌落与骤升、电压不平衡等电能质量问题对双馈感应发电机(DFIG)风电系统的影响,在对多种统一电能质量调节器(UPQC)拓扑结构研究对比和九开关变换器建模分析的基础上,提出一种应用于双馈风电系统的九开关型UPQC方案。在对UPQC电压、电流补偿单元运算电路建模的基础上,设计相应的控制策略。按照电网工况,设定谐波电流补偿、轻度电压补偿、重度电压补偿3种工作模式,优化UPQC运行方案。仿真与实验结果表明,九开关型UPQC可以有效治理电压、电流谐波,消除电压偏差与相位跳变,提高DFIG机端电能质量,使机组可以在多种故障电压工况下实现柔性故障穿越。     

Management of reactive power sharing & power quality improvement with SRF-PAC based UPQC under unbalanced source voltage condition

This paper is proposed to establish a new control algorithm for UPQC (unified power quality conditioner) to improve power quality and manage effectively equal reactive power sharing between shunt and series inverter of UPQC under unbalanced source voltage condition. The extraction of instantaneous power angle for reactive power sharing faces difficulty with unbalanced source voltage condition. This paper presents a new SRF (synchronous reference frame) based PAC (power angle control) method using decoupled load current parameters for efficient utilization and coordination of UPQC inverters. The proposed controller contributes in improvement of source current and load voltage harmonic profile, provides efficient way of load reactive power compensation and load voltage compensation for sag, swell and unbalanced condition. Effect of source voltage variations in the form of sag, swell or unbalancing on variable power angle estimation and reactive power calculations are also validated through a mathematical analysis. SRF based PAC control approach and PAC based UVT (unit vector template) control approach is adapted for estimating the reference signals of shunt and series inverter respectively and thus reducing the need of extra computation. The simulation and experimental analysis is carried out using Matlab/Simulink software package for computer simulation and a dSPACE based experimental setup for real time verifications.     

一种电压源型有源电力滤波器的新型控制方法

研究了电压源型有源电力滤波器、电源及非线性负载三者之间的能量交换机理,分析了变流器直流侧电容电压的稳定问题,提出了维持直流侧电容电压稳定的新方法。在此基础上提出了一种电压源型有源电力滤波器的新型控制方法,详细推导了控制方程。该方法无需检测三相负载电流和三相输入电压,无需计算参考电流、无功电流和谐波电流;只需检测两相电源电流和直流侧电容电压,通过简单运算就可直接求出每个开关周期内各开关的占空比,实现滤波器的控制。仿真研究结果表明新型控制方法能有效补偿谐波电流和无功电流,抑制负载不对称。     

Novel schemes used for estimation of power system harmonics and their elimination in a three-phase distribution system

Estimation of power system harmonics and their elimination is an interdisciplinary area of interest for many researchers. This paper presents Variable Step Size Least Mean Square (VSS-LMS) approach for harmonics estimation and Shunt Active Power Filter (SAPF) with two-level Hysteresis Current Control (HCC) technique for their elimination in a three-phase distribution system. In the estimation process, the weight is updated using VSS-LMS algorithm. Harmonics components are estimated from the updated weights. In order to mitigate harmonics produced by the nonlinear load connected in a three-phase distribution system, SAPF with two-level HCC is proposed. A three-phase insulated gate bipolar transistor (IGBT) based current controlled voltage source inverter (CC VSI) with a dc bus capacitor is used as an active power filter. The first step is to calculate SAPF reference currents from the sensed nonlinear load currents by applying the synchronous detection method and then the reference currents are fed to the proposed controller for generation of switching signals. The nonlinear load consists of one three-phase and one single-phase diode rectifier feeding R–L load, so that the effectiveness of the two-level HCC scheme to compensate for unbalanced nonlinear load can be tested. Various simulation results are presented to verify the good behavior of the SAPF with proposed two levels HCC.     

A novel approach of reference current generation for power quality improvement in three-phase, three-wire distribution system using DSTATCOM

This paper presents a novel approach based on an improved instantaneous active and reactive current component theory for generating reference currents for distribution static compensator (DSTATCOM). Three-phase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme. The performance of the DSTATCOM using the proposed control strategy has been evaluated under various source and load conditions. The performance of the proposed control strategy has been evaluated in terms of load balancing, reactive power compensation, compensator rating and harmonic mitigation. A three-phase, three-wire distribution system supplying star connected linear as well as non-linear unbalanced load is considered for simulation study. The detailed simulation results using MATLAB/SIMULINK software are presented to support the feasibility of proposed control strategy.     

Control strategies for harmonic mitigation and power factor correction using shunt active filter under various source voltage conditions

This paper gives a new insight into the concept of load compensation using shunt active filter (SAF) under ideal and non-ideal source voltage conditions. A novel approach based on an improved instantaneous active and reactive current component method is proposed. The performance of the proposed control strategy has been compared with instantaneous reactive power theory, symmetrical component theory and dq theory. SAF has been realized by three-phase voltage source converter. Reference currents generated by control strategies has been tracked by a SAF in a hysteresis band control scheme. The performance of the proposed scheme is evaluated in terms of reactive power compensation, reduction in magnitude of source currents, compensator currents, and harmonic compensation as per IEEE-519 standard. To ascertain the viability of the proposed control algorithm, the performance is evaluated under different source voltage conditions with the IEEE Standard-1459 power definitions. Variation in magnitude as well as harmonic content of source voltage has been considered. Under balanced sinusoidal source voltage condition, all control strategies congregate to similar results. Under unbalanced sinusoidal source voltage condition, dq theory and proposed theory have shown similar performance. However, under distorted source voltage conditions, an improved instantaneous active and reactive current component theory presents superior performance. A three-phase, three-wire distribution system supplying non-linear load is considered for simulation study. Simulation results from a complete model of SAF are presented to validate and compare the control strategies.     

一种基于链式结构UPQC的电气化铁路同相供电方案研究

介绍了一种基于统一电能质量控制器（UPQC）的电气化铁路同相供电方案,通过对UPQC的主电路结构、功能和控制方法的详细分析,指出了该控制器相对于现有其他方案的优点,最后对同相供电系统在电力机车处于正常运行和再生制动这2种典型工况时的补偿效果进行了仿真,仿真结果表明,基于UPQC的同相供电系统能解决电气化铁路牵引变电所存在的三相电压不平衡、电压波动、功率因数低下以及谐波污染等问题,UPQC与能量存储系统ESS相结合,还能很好地解决机车再生制动能量回馈等问题。     

DVR的不平衡浪涌和过电压控制

讨论无串联隔离变压器的动态电压调节器(DVR)在不平衡电压浪涌或过电压情况下的补偿问题。使用不可控整流为直流侧电容充电的DVR,在补偿时只允许其向系统注入有功功率。在浪涌或过电压发生时,DVR可能发生从系统吸收有功功率的情况,如果仍然使用传统的同相或相位不变电压注入控制方法,将导致直流侧电容电压迅速升高,可能损坏开关器件或储能单元。利用最小能量补偿控制方法也不能完全解决该问题,因而提出一种单向功率流动控制算法。该算法通过将参考电压旋转一定的角度,使DVR无论在3相平衡与不平衡浪涌或过电压的情况下,都不从配电系统吸收有功,同时能将负荷电压补偿为3相平衡且达到正弦的额定值。该算法加入对DVR最大补偿极限的考虑,以确保注入补偿电压不超过DVR的补偿极限。文中对直流母线电压不可避免的泵升问题提出了缓冲控制策略。最后,仿真结果验证了算法的正确性及有效性。